package lab3;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.*;


public class MyBatisUtil {
    private static ThreadLocal<SqlSession> threadLocal = new
            ThreadLocal<SqlSession>();
    private static SqlSessionFactory sqlSessionFactory;

    //静态块加载src目录下的mybatis配置文件

    static{
        try {
            Reader reader = Resources.getResourceAsReader(MyBatisUtil.class.getClassLoader(), "mybatis.xml");
            SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
            sqlSessionFactory = sqlSessionFactoryBuilder.build(reader);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /*
     * 禁止外界通过new方法创建
     */
    private MyBatisUtil(){}

    /*
     * 获取sqlsession
     */
    public static SqlSession getSqlSession()
    {
        //从当前线程中获取sqlSession对象
        SqlSession sqlSession = threadLocal.get();

        //判断SqlSession对象是否为空
        if(sqlSession==null)
        {
            //在SqlSessionFactory对象非空的情况下，获取SqlSession对象
            sqlSession = sqlSessionFactory.openSession();
            //将SqlSession对象与当前线程绑定在一起
            threadLocal.set(sqlSession);
        }

        return sqlSession;
    }

    /*
     * 关闭sqlsession与当前线程分开
     */
    public static void closeSqlSession()
    {
        //从当前线程中获取SqlSession对象
        SqlSession sqlSession = threadLocal.get();

        if(sqlSession != null)
        {
            //关闭SqlSession对象
            sqlSession.close();
            //分开当前线程与SqlSession对象的关系，目的是尽早进行垃圾回收
            threadLocal.remove();
        }
    }
}
